Non-imaging optics have a wide variety of applications throughout scientific, industrial, and military fields. In contrast to traditional imaging optics, non-imaging optics do not form an image of a source of electromagnetic radiation. Instead, non-imaging optics optimize the transfer of luminous power. For instance, non-imaging optics are often used in solar energy conversion systems.
In many optical systems it is desirable to have a wide field of view. For example, many telescopes have a large entrance aperture to permit imaging of a distant scene. This requires a large imaging detector or a short focal length such that light from the extremes of the field of view is focused on the detector. Use of a large detector increases the size, weight, power, and cost of the system. Use of a shorter focal length limits the optical system aperture diameter which limits the operating range of the system.
FIGS. 1A and 1B illustrate a known wide field of view non-imaging optical system. Electromagnetic radiation 100 propagating along an input optical path 102 is received at a focusing lens 104, and focused on a detector 106. FIG. 1B demonstrates a front view of the detector 106 shown in FIG. 1A. The radiation received along the input optical path 102 is focused at the center of the detector 106 to form an image 108. In contrast, radiation that is received at an off-set angle θ from the optical path 102 (radiation shown as line 110) is displaced from the center of the detector 106 and not viewable when the angle θ exceeds the acceptance angle of the focusing lens 104 and detector 106.
Conventionally, collecting more off-axis light is addressed by increasing the size of the detector until all (or most) of the incident electromagnetic radiation is viewable by the detector. However, such conventional approaches increase the weight and operational costs of the optical system, and are impractical in many applications. Other attempts to address this issue have suggested shortening the focal length of the optical system. However, such a solution would impact the characteristics of the optical elements and limit the operating range of the system. For instance, a known system having a 0.2 mm diameter detector may not image incident light if the incident light is as little as one degree off-axis of the optical axis. Further attempts have suggested decreasing the diameter of the aperture. However, such a solution would impact the ability to operate at long ranges. The same trades are performed for imaging and non-imaging optical systems alike.